Method and apparatus utilizing time-expanded pulse sequences for distance measurement in a radar
First Claim
1. A method of processing radar echo pulse sequences having steep pulse flanks and a predetermined sequence frequency, comprising the steps of:
- generating an auxiliary pulse sequence of a sequence frequency that differs slightly from said predetermined sequence frequency;
multiplying the pulses of a radar echo pulse sequence by the pulses of said auxiliary pulse frequency;
integrating the product signal produced by the multiplying step and thereby suppressing high frequency signal components and obtaining time-expanded radar signals, andutilizing said time-expanded radar signals for control of indicator means as if said time-expanded signals were directly detected radar signals.
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Abstract
Pulse sequences from a radar receiver respectively made up of successive start pulses and of successive echo pulses from one or more targets are expanded in time by multiplication with an auxiliary pulse sequence differing slightly in repetition rate from the start pulse sequence. This enables circuits to be used with a lower degree of time resolution that would otherwise be needed, at the cost of proportionally reducing the number of individual measurements of the target distance, a cost which is of no substantial consequence in an anti-collision radar where the closing rates are small compared to the pulse repetition rate. A time-expanded sequence of reference pulses is similarly produced from the oscillator controlling the repetition of the radar pulses and the auxiliary oscillator in order to make the measurements independent of signal propagation times within these circuits. The time-expanded pulses to be evaluated are differentiated and the null passage instant of the differentiated pulses is used to find the maximum amplitude of the pulses and to determine which pulses should be disregarded on the basis of amplitude discrimination. A range gate controlled with reference to the velocity of the vehicle in which the radar is mounted, in combination with certain other factors, is used to exclude interference from irrevalent targets.
39 Citations
8 Claims
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1. A method of processing radar echo pulse sequences having steep pulse flanks and a predetermined sequence frequency, comprising the steps of:
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generating an auxiliary pulse sequence of a sequence frequency that differs slightly from said predetermined sequence frequency; multiplying the pulses of a radar echo pulse sequence by the pulses of said auxiliary pulse frequency; integrating the product signal produced by the multiplying step and thereby suppressing high frequency signal components and obtaining time-expanded radar signals, and utilizing said time-expanded radar signals for control of indicator means as if said time-expanded signals were directly detected radar signals. - View Dependent Claims (2, 3, 4)
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5. In a pulse radar system which comprises means for generating and transmitting radar pulses, for receiving radar echo pulses and for evaluating or displaying a relation of the time of arrival of echo pulses and the time of transmission of corresponding radar pulses, the improvement which consists of the provision of:
a time scale expansion circuit interposed between the means for receiving radar echo pulses and the means for evaluating or displaying a relation of the time of arrival of echo pulses and the time of transmission of corresponding radar pulses, which time scale expansion circuit comprises oscillator means for generating an auxiliary pulse sequence having a pulse repetition rate differing slightly from that of said transmitted radar pulses, a multiplier circuit having one input connected to the output of the radar pulse receiver and another input connected to the output of said auxiliary pulse sequence oscillator means, an integrator having its input connected to the output of said multiplier circuit and having an output supplying a sequence of radar echo pulses of expanded time scale. - View Dependent Claims (6, 7, 8)
Specification